1. Field of the Invention
This invention relates generally to automated data-storage libraries and, in particular, to a lockout mechanism for ensuring that a data cartridge is inserted correctly into the receiving cell of the input/output station of a library.
2. Description of the Prior Art
The portability of magnetic tape cartridges makes it possible to store them in readily accessible multi-cell libraries, so that large amounts of data can be saved and retrieved at will using automated equipment. When, for example, a particular cartridge is required for use in a computer's tape drive, the unit is retrieved by a robot from the cell where it has been stored in a library and it is automatically loaded for processing.
Cartridges are initially placed into libraries manually through input/output stations which consist of stacks of individual through-slots with an exterior opening adapted to receive a cartridge of a predetermined size and configuration. For example, FIG. 1 illustrates an IBM 3584 Automated Library that incorporates an I/O station 10 with a cartridge 12 inserted half-way into a receiving through-slot 14. Each slot has also an interior opening (not shown) through which the cartridge is removed by a robot for automated placement in a library storage cell or magazine. The picker mechanism through which each cartridge is transferred includes gripper arms that hold the cartridge and guide it in and out of the I/O station, and similarly in and out of the library cell, computer peripheral, or other device being used. The cartridges have retaining features that permit gripper arms to latch on to the cartridge by means of appropriate locating and gripping notches or equivalent structural features built into the case of the cartridge.
In operation, each cartridge 12 is initially inserted manually by an operator into a slot 14 of a receiving cell in the I/O station. The cartridge must be positioned correctly in order for the gripper arms to be able to retrieve it from the other side of the cell. Improper orientation of the cartridge would cause a failure of the automated system. The problem is worse with libraries that operate with multiple types of cartridges.
Two of the cartridge formats most widely used currently around the world are the so called DLT (digital linear tape) and LTO (linear tape open) formats, each are characterized in detail by corresponding ECMA (European Computer Manufacturers Association) 286 and 319 standards. Some additional cartridge formats are the IBM 3592 and the IBM 3590 formats. A mixed-media library, such as IBM's 3584, may utilize cartridges conforming to some or all of these formats and an I/O station must be able to distinguish between the different types of cartridges.
Each cartridge format features prescribed structural attributes adapted to function with conforming standard features in the automated mechanisms of a corresponding drive, picker and library system. For example, a typical DLT format cartridge 20, such as IBM's DLT IV Cartridge illustrated in FIG. 2, is characterized by a hinged door 22 on the front side 14 of the cartridge. When the DLT cartridge is inserted into a drive, a stationary device penetrates a gap 26 in the door hinge 28 and presses against a spring-loaded latch 30 to automatically release the door 22 and swing it open toward the front of the cartridge. As a result, the tape's leader inside the cartridge (not seen) can be accessed by the drive's mechanism. As the door 22 opens, the door hinge 28 rotates inwardly toward the right side 32 of the cartridge. Accordingly, the right side of the DLT cartridge 20 features a progressively deepening cavity 34 designed to accommodate the door hinge 28 when the door 22 is fully open. The shallower portion of the cavity 34 also features two ribs 36.
Thus, the right side 32 of the DLT cartridge contains several pronounced structural features that distinguish it from all other sides, as well as from every side of LTO, 3592, and 3590 cartridges. When a DLT cartridge is inserted in an I/O station by an operator, it must be placed top-side up and with the door 22 facing the exterior of the station; otherwise, the library picker cannot properly grab and retain the cartridge, and the picker may become disabled causing the automated library to go off-line and the stored data to become inaccessible. This possibility of failure is unacceptable in today's world of uninterrupted-service demand.
U.S. Pat. No. 6,141,180, issued to Smith, describes a pivoting lockout that prevents the incorrect placement of a cartridge into a receiving device, such as a tape magazine, a library or a mail slot. The lockout consists of a hinged member with a leading and a trailing edge protruding into the sleeve to be occupied by the cartridge when it is placed in the receiving device. Therefore, the cartridge can be successfully introduced into the device only one way, when the side containing the cavity is facing the hinged lockout member. Because of its configuration and placement, the lockout member is able to clear the ribs 36 and to fit into the cavity 34 of the cartridge (refer to FIG. 2 above) as the cartridge is pushed into the sleeve of the receiving device. Thus, the lockout of the invention prevents the complete insertion of the cartridge unless it is oriented correctly.
The Smith lockout device is not designed for a pass-through sleeve of the type present in I/O stations. It is only concerned with ensuring that the cartridge is placed correctly in a receiving cell from which it is to be extracted later in reverse direction. The present invention provides a new design for a lockout mechanism that may be used with pass-through sleeves and is therefore suitable for use in input/output stations.
Other methods of locking out improperly oriented cartridges sometimes involve the use of an external part of the I/O station to move a mechanism, e.g. a door or toggle bracket. It would be advantageous to have a fully self-contained mechanism for locking incorrect cartridges that does not require the use of parts that are external to the cell.
Other mechanisms to control cartridge orientation do not work well when various cartridges have a large disparity in size, such as between 3592 and LTO cartridges. These mechanisms attempt to locate a hole or void in the side of the cartridge. When a void locator falls into one of these holes, the cartridge is accepted into the cell. However, if a cartridge which is significantly smaller than the cartridge intended for the cell is inserted, the void locator will not prevent it from being inserted. Accordingly, it would be advantageous to have a device for locking out cartridges that are significantly smaller than the intended cartridge.
Yet another method of preventing the picker from grabbing an incorrect cartridge is to use an optical system to read labels placed on the cartridges. If the label cannot be found, is illegible, or does not include the expected information, the picker will refuse the cartridge. However, labels are prone to damage and falling off of cartridges. Additionally, an incorrect label may be placed on a non-compatible cartridge, incorrectly identifying it as an acceptable cartridge and allowing the picker to attempt to grip it. Therefore, it would be advantageous to provide a means for locking out non-compatible cartridges that does not rely on labels.
Each cartridge format has a set of physical characteristics that distinguishes it from other types of cartridges. Illustrated in FIG. 3, a 3592 cartridge 38 is defined by its size, its shape, and an angled recess 40 in the center of the lower portion of the front face 42 of the cartridge 44. While a mixed-media library, such as the IBM 3584, is designed to work with multiple cartridge formats, each slot 14 (FIG. 1) is usually adapted to accommodate only a single type of cartridge. Inserting the wrong type of cartridge into a slot may damage the picker, causing the library to go off-line. Additionally, data stored on the improperly inserted cartridge may be destroyed. Accordingly, it would be very desirable to have a mechanism that prevents the incorrect placement of a 3592 cartridge or the placement of another cartridge into the receiving slots of an I/O station designed to handle only 3592 cartridges.